Grommet hub



FIG. 1 is a front side view of the grommet hub;

FIG. 2 is a left side view thereof;

FIG. 3 is a right side view thereof;

FIG. 4 is a top side view thereof;

FIG. 5 is a bottom side view thereof;

FIG. 6 is a rear view thereof;

FIG. 7 is a top isometric view thereof; and,

FIG. 8 is a bottom isometric view thereof.

The broken lines represent the portions of the design that form no part of the claimed design. 

The ornamental design for a grommet hub, as shown and described. 